T Sql Unique Constraint Multiple Columns

T Sql Unique Constraint Multiple Columns. Different from PRIMARY KEY constraints, UNIQUE constraints allow NULL. Moreover, UNIQUE constraints treat the NULL as a regular value, therefore.

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When two rows are inserted with NULL values into UNIQUE index column, SQL Server throws an error saying that two NULL values are same and are duplicates. I want the unique constraint to be on "csaType" and "equipmentDeliverDate" columns combined! Unique construct returns true only if the sub query has no duplicate tuples, else it return false.

Recently I came across a requirement to create a unique column which should allow multiple nulls and apply uniqueness on anything other than null.

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For example, the following SQL query creates a new table called CUSTOMERS and adds five columns. For example, if we want to make sure that the Employee or a Then you can use the ALTER TABLE Statement to Drop the unique constraint. Cannot --INSERT duplicate KEY IN OBJECT 'dbo.